Reading or Math Skill Set for 3-Yr-Old Birthday?

My toddler is turning three this fall. Should I get him part 1 of the reading skill set or part 1 of the math skill set for his birthday?

Then, would you suggest part 2 of the same skill set for a Christmas gift? OR would it be better to have both part 1 of reading and part 1 of math during his 3-year-old year? Then buy both part 2s when he is 4 years old?

OR do I just spend all my money now and buy both the full sets for bday and Christmas this year? 😅